EP1710010A1 - Process and device for the selective catalytic reduction of exhaust gases from a combustion engine - Google Patents

Process and device for the selective catalytic reduction of exhaust gases from a combustion engine Download PDF

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Publication number
EP1710010A1
EP1710010A1 EP06006664A EP06006664A EP1710010A1 EP 1710010 A1 EP1710010 A1 EP 1710010A1 EP 06006664 A EP06006664 A EP 06006664A EP 06006664 A EP06006664 A EP 06006664A EP 1710010 A1 EP1710010 A1 EP 1710010A1
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EP
European Patent Office
Prior art keywords
reducing agent
sensor
concentration
metering device
scr catalyst
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP06006664A
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German (de)
French (fr)
Inventor
Uwe Gärtner
Peter Kozuch
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Mercedes Benz Group AG
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DaimlerChrysler AG
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Publication of EP1710010A1 publication Critical patent/EP1710010A1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F01N3/208—Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9431—Processes characterised by a specific device
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9495—Controlling the catalytic process
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/105—General auxiliary catalysts, e.g. upstream or downstream of the main catalyst
    • F01N3/106—Auxiliary oxidation catalysts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/30—Arrangements for supply of additional air
    • F01N3/32—Arrangements for supply of additional air using air pump
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
    • F01N2560/021—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting ammonia NH3
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
    • F01N2560/022—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting CO or CO2
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/14—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics having more than one sensor of one kind
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/14—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust gas
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Definitions

  • the invention relates to an apparatus and a method for the selective catalytic reduction of exhaust gases from an internal combustion engine, in particular a direct-injection diesel engine.
  • SCR catalysts for the selective catalytic reduction of nitrogen oxides are generally used today.
  • NH 3 or NH 3 releasing substance as a reducing agent with the support of compressed air or undiluted in liquid form before the SCR catalyst in the exhaust system injected.
  • the ammonia is used in the SCR catalyst for the reduction of nitrogen oxides.
  • NH 3 or NH 3 releasing substances as a reducing agent is controlled by a control unit.
  • a control unit for example, this describes the DE 41 17 143 A1 a method for the selective catalytic reduction of exhaust gases from automotive diesel engines, in which the clocked superstoichiometric addition of NH 3 or NH 3 releasing substances by means of a calculation of NH 3 concentration in the catalyst bed from known sizes of the diesel engine and the exhaust aftertreatment system is controlled.
  • the DE 42 17 552 C1 proposes, for selective catalytic reduction of exhaust gases from an internal combustion engine, the use of a first NH 3 sensor for detecting an NH 3 concentration in the exhaust gas after the SCR catalyst and a second NH 3 sensor for detecting NH 3 adsorption in the catalyst bed; to control the addition of the NH 3 reducing agent based on the measured NH 3 sizes.
  • the present invention is an object of the invention to provide an improved apparatus and an improved method for the selective catalytic reduction of exhaust gases from an internal combustion engine.
  • the device for the selective catalytic reduction of exhaust gases from an internal combustion engine contains a catalyst for the selective catalytic reduction of nitrogen oxides from exhaust gases of an internal combustion engine; a reducing agent metering device disposed upstream of the SCR catalyst for adding a urea-water solution as a reducing agent; and a controller for driving the reducing agent metering device.
  • a first CO 2 sensor for detecting a CO 2 concentration upstream of the reducing agent metering device and a second CO 2 sensor for detecting a CO 2 concentration downstream of the reducing agent metering device are further arranged, and the controller controls the reducing agent metering device depending on a detected by the first and the second CO 2 sensor CO 2 concentration difference.
  • the control device can also act as a control device, which acts on the reducing agent metering device as an adjusting device, so that the reducing agent addition to the exhaust gas can be regulated on the basis of signals from the CO 2 sensors.
  • the addition of reducing agent can also be carried out in a controlled manner on the basis of characteristic curves or characteristic diagrams which are available to the control unit.
  • the amount of reducing agent to be metered is taken from the characteristic curves or characteristic diagrams and the metering device is activated accordingly.
  • a superstoichiometric addition of the reducing agent takes place.
  • HWL urea-water solution
  • This by-product of the hydrolysis namely carbon dioxide, is now used as a parameter for controlling the reducing agent metering device.
  • the actually injected mass of the HWL can be calculated from the known exhaust gas mass flow. Based on this information, the controller can then determine the metering HWL amount and control the metering optimally.
  • the second CO 2 sensor is provided at a distance downstream of the reducing agent metering device such that complete hydrolysis of the reducing agent has taken place on the second CO 2 sensor.
  • the second CO 2 sensor can be arranged both upstream of the SCR catalytic converter and downstream of the SCR catalytic converter, since the reactions in the SCR catalytic converter do not influence the CO 2 concentration in the exhaust gas flow.
  • the arrangement of the second CO 2 sensor downstream of the SCR catalyst is advantageous because of the thus longer hydrolysis distance for the reducing agent.
  • the first CO 2 sensor may also be a virtual sensor which calculates the CO 2 concentration from the controller known variables.
  • the first and the second CO 2 sensor are designed as a CO 2 difference sensor with high sensitivity. This variant is particularly advantageous when the second CO 2 sensor measured CO 2 concentration is only slightly higher than that detected by the first CO 2 sensor.
  • an NH 3 sensor for detecting an NH 3 concentration downstream of the SCR catalyst is further arranged.
  • an NH 3 sensor arranged behind the SCR catalytic converter for detecting the NH 3 slip after the SCR catalytic converter it is possible to quantify the proportion of ammonia reacted or stored in the SCR catalytic converter.
  • a known oxidation catalyst is preferably also provided upstream of the reducing agent metering device.
  • a reducing agent nozzle of the reducing agent metering device is also associated with a compressed air nozzle to inject the reducing agent with the aid of compressed air.
  • FIG. 1 the structure of an exhaust aftertreatment system of an internal combustion engine 10, in particular a direct-injection diesel engine, according to an embodiment of the invention is schematically illustrated.
  • the internal combustion engine is the reference numeral 10, an exhaust pipe the reference numeral 12, an oxidation catalyst, the reference numeral 14 and an SCR catalyst, the reference numeral 30 assigned.
  • the structure and operation of the internal combustion engine 10, the oxidation catalyst 14 and the SCR catalyst 30 are known in the art and will not be explained in detail here, since they are not the subject of the invention.
  • a reducing agent metering device 15 Upstream of the SCR catalyst 30 for the selective catalytic reduction of nitrogen oxides in the exhaust stream from the internal combustion engine 10, a reducing agent metering device 15 is provided.
  • This reducing agent metering device 15 comprises, for example, a reducing agent tank 20, a feed pump 22, a check valve 24 and a reducing agent nozzle 16 protruding into the exhaust gas line 12.
  • the feed pump 22 and the check valve 24 are actuated by a control unit 38.
  • the reducing agent nozzle 16 in the exhaust pipe 12 is associated with a compressed air nozzle 18 which is connected via a check valve 28 to a compressed air source 26.
  • the reducing agent is preferably injected into the exhaust pipe 12 with the aid of compressed air.
  • HWL urea-water solution
  • a first CO 2 sensor 32 upstream of the reducing agent nozzle 16 of the reducing agent metering device 15 and a second CO 2 sensor 34 downstream of the reducing agent 16 each for detecting a CO 2 concentration are arranged.
  • the second CO 2 sensor 34 is preferably arranged at such a distance behind the reducing agent nozzle 16, which is required for complete hydrolysis of the injected HWL. From the difference between the CO 2 concentrations before and before the reducing agent nozzle 16, it is possible to simply calculate the injected mass of the HWL from the known exhaust gas mass flow in the exhaust gas line 12, assuming complete hydrolysis of the HWL. Based on this information, the controller 38 then controls the reductant metering device 15.
  • control unit 38 is also supplied with measured values of the internal combustion engine 10 and one or more temperature sensors 40 in the exhaust gas line 12.
  • the invention is suitable Sensors 32, 34 also for monitoring the quality of hydrolysis in the exhaust aftertreatment system.
  • the second CO 2 sensor 34 is not disposed upstream of the SCR catalyst 30, but provided thereafter, as indicated by the reference numeral 34 'in Fig. 1.
  • the arrangement of the second CO 2 sensor 34 'behind the SCR catalyst 30, the hydrolysis distance is extended to the measurement of the CO 2 concentration, whereby the measurement accuracy can be increased.
  • the CO 2 concentration is not affected by the reactions in the SCR catalyst 30.
  • an NH 3 sensor 36 is also provided downstream of the SCR catalytic converter 30 in the exemplary embodiment of FIG. 1, for detecting an NH 3 slip after the SCR catalytic converter 30, the measured value of which is likewise fed to the control unit 38.
  • This additional NH 3 sensor 36 makes it possible to quantify the proportion of ammonia reacted or stored in the SCR catalytic converter 30. If the slip over the NH 3 sensor 36 is kept constant, the SCR catalyst 30 can no longer store ammonia.
  • the difference of the NH 3 concentrations before and after the SCR catalyst 30 is thus a direct measure of the conversion in the SCR catalyst 30 or provides statements about the state (eg degree of conversion over life) of the SCR catalyst 30 calculated NH 3 concentration before the SCR catalyst 30 from the above CO 2 measurement.
  • the first and second CO 2 sensors 32 and 34 and 34 'in FIG. 1 are formed as separate sensors.
  • a CO 2 difference sensor with high sensitivity whose measuring points correspond to the sensor positions of the embodiment described above.
  • the use of such a CO 2 differential sensor can provide significant benefits if the increase in CO 2 concentration at the location of the second CO 2 sensor 34, 34 'is relatively small compared to the location of the first CO 2 sensor 32.
  • first CO 2 sensor 32 calculates the CO 2 concentration in front of the reducing agent metering device 15 on the assumption of complete combustion of the fuel injected in the internal combustion engine 10 from the variables air mass and fuel mass known in the control unit 38. This assumption is permissible because in the diesel engine 10 only a very small proportion of the fuel is not reacted and emitted in the form of HC and CO emissions. If the first CO 2 sensor 32 is also provided downstream of an oxidation catalytic converter 14, the CO 2 concentration there also contains the carbon dioxide from the post-oxidation of the unburned exhaust gas components in the oxidation catalytic converter 14.

Abstract

Reducing nitrogen oxides in the exhaust gas of an internal combustion engine using a selective catalytic reduction (SCR) catalyst comprises injecting a urea-water solution as reducing agent upstream of the SCR catalyst, measuring the carbon dioxide concentration upstream and downstream of the injection point and adjusting the amount of reducing agent injected as a function of the difference between the two carbon dioxide concentrations. An independent claim is also included for apparatus for reducing nitrogen oxides in the exhaust gas of an internal combustion engine, comprising a selective catalytic reduction (SCR) catalyst (30), a metering device (15) for injecting a urea-water solution as reducing agent, a first carbon dioxide (CO2) sensor (32) upstream of the metering device, a second CO2 sensor (34, 34') downstream of the metering device, and a control unit (38) for controlling the metering device in response to a CO2 concentration difference measured by the two sensors.

Description

Die Erfindung betrifft eine Vorrichtung und ein Verfahren zur selektiven katalytischen Reduktion von Abgasen aus einem Verbrennungsmotor, insbesondere einem direkteinspritzenden Dieselmotor.The invention relates to an apparatus and a method for the selective catalytic reduction of exhaust gases from an internal combustion engine, in particular a direct-injection diesel engine.

Da der Hochdruckprozess in einem direkteinspritzenden Dieselmotor immer überstöchiometrisch abläuft, sind die Konzentrationen von unverbrannten Kohlenwasserstoffen und Kohlenstoffmonoxid im Abgas bei den heute üblichen hohen Abgasrückführraten prinzipbedingt niedrig. Zudem lassen sich diese Konzentrationen trotz der niedrigen Abgastemperatur von Dieselmotoren unter Sauerstoffüberschuss durch moderne Oxidationskatalysatoren nahezu vollständig nachoxidieren.Since the high-pressure process in a direct-injection diesel engine always proceeds more than stoichiometrically, the concentrations of unburned hydrocarbons and carbon monoxide in the exhaust gas are inherently low at today's high exhaust gas recirculation rates. In addition, despite the low exhaust gas temperature of diesel engines under excess oxygen, these concentrations can be almost completely post-oxidized by modern oxidation catalysts.

Problematisch ist demgegenüber die Abgasnachbehandlung von Stickoxid- und Rußemissionen. Zum Senken dieser gesundheitsgefährlichen Schadstoffkomponenten werden heutzutage im Allgemeinen so genannte SCR-Katalysatoren zur selektiven katalytischen Reduktion von Stickoxiden eingesetzt. Hierbei wird NH3 oder ein NH3 freisetzender Stoff als Reduktionsmittel mit Unterstützung von Druckluft oder unverdünnt in flüssiger Form vor dem SCR-Katalysator in den Abgastrakt eingedüst. Das Ammoniak wird im SCR-Katalysator zur Reduktion der Stickoxide verwendet.In contrast, the exhaust aftertreatment of nitrogen oxide and soot emissions is problematic. To lower these hazardous pollutant components, so-called SCR catalysts for the selective catalytic reduction of nitrogen oxides are generally used today. In this case, NH 3 or NH 3 releasing substance as a reducing agent with the support of compressed air or undiluted in liquid form before the SCR catalyst in the exhaust system injected. The ammonia is used in the SCR catalyst for the reduction of nitrogen oxides.

Die Eindüsung des NH3 oder von NH3 freisetzenden Stoffen als Reduktionsmittel wird durch ein Steuergerät geregelt. So beschreibt zum Beispiel die DE 41 17 143 A1 ein Verfahren zur selektiven katalytischen Reduktion von Abgasen aus Kraftfahrzeugdieselmotoren, bei dem die getaktete überstöchiometrische Zugabe von NH3 oder NH3 freisetzenden Stoffen mittels einer Berechnung einer NH3-Konzentration im Katalysatorbett aus bekannten Größen des Dieselmotors und des Abgasnachbehandlungssystems geregelt wird.The injection of NH 3 or NH 3 releasing substances as a reducing agent is controlled by a control unit. For example, this describes the DE 41 17 143 A1 a method for the selective catalytic reduction of exhaust gases from automotive diesel engines, in which the clocked superstoichiometric addition of NH 3 or NH 3 releasing substances by means of a calculation of NH 3 concentration in the catalyst bed from known sizes of the diesel engine and the exhaust aftertreatment system is controlled.

Die DE 42 17 552 C1 schlägt zur selektiven katalytischen Reduktion von Abgasen aus einem Verbrennungsmotor die Verwendung eines ersten NH3-Sensors zum Erfassen einer NH3-Konzentration im Abgas nach dem SCR-Katalysator und eines zweiten NH3-Sensors zum Erfassen einer NH3-Adsorption im Katalysatorbett vor, um basierend auf den gemessenen NH3-Größen die Zugabe des NH3-Reduktionsmittels zu regeln.The DE 42 17 552 C1 proposes, for selective catalytic reduction of exhaust gases from an internal combustion engine, the use of a first NH 3 sensor for detecting an NH 3 concentration in the exhaust gas after the SCR catalyst and a second NH 3 sensor for detecting NH 3 adsorption in the catalyst bed; to control the addition of the NH 3 reducing agent based on the measured NH 3 sizes.

Im Fall der DE 198 28 928 A1 wird schließlich die selektive katalytische Reduktion von Abgasen aus einem Verbrennungsmotor mittels eines NOx-Sensors stromab des SCR-Katalysators überwacht.In the case of DE 198 28 928 A1 Finally, the selective catalytic reduction of exhaust gases from an internal combustion engine by means of a NO x sensor downstream of the SCR catalyst is monitored.

Der vorliegenden Erfindung liegt demgegenüber die Aufgabe zugrunde, eine verbesserte Vorrichtung und ein verbessertes Verfahren zur selektiven katalytischen Reduktion von Abgasen aus einem Verbrennungsmotor bereitzustellen.The present invention is an object of the invention to provide an improved apparatus and an improved method for the selective catalytic reduction of exhaust gases from an internal combustion engine.

Diese Aufgabe wird durch eine Vorrichtung mit den Merkmalen des Anspruchs 1 bzw. ein Verfahren mit den Merkmalen des Anspruchs 10 gelöst. Vorteilhafte Ausgestaltungen und Weiterbildungen der Erfindung sind Gegenstand der jeweiligen Unteransprüche.This object is achieved by a device having the features of claim 1 and a method having the features of claim 10. Advantageous embodiments and developments The invention are the subject of the respective subclaims.

Die Vorrichtung zur selektiven katalytischen Reduktion von Abgasen aus einem Verbrennungsmotor enthält einen Katalysator zur selektiven katalytischen Reduktion von Stickoxiden aus Abgasen eines Verbrennungsmotors; eine Reduktionsmittel-Dosiervorrichtung, die stromauf des SCR-Katalysators angeordnet ist, zum Zugeben einer Harnstoff-Wasser-Lösung als Reduktionsmittel; und ein Steuergerät zum Ansteuern der Reduktionsmittel-Dosiervorrichtung. Erfindungsgemäß sind ferner ein erster CO2-Sensor zum Erfassen einer CO2-Konzentration stromauf der Reduktionsmittel-Dosiervorrichtung und ein zweiter CO2-Sensor zum Erfassen einer CO2-Konzentration stromab der Reduktionsmittel-Dosiervorrichtung angeordnet, und das Steuergerät steuert die Reduktionsmittel-Dosiervorrichtung in Abhängigkeit von einer durch den ersten und den zweiten CO2-Sensor erfassten CO2-Konzentrationsdifferenz an. Auf diese Weise kann das Reduktionsmittel bedarfsgerecht zugemessen werden. Dabei kann das Steuergerät auch als Regeleinrichtung wirken, welche auf die Reduktionsmittel-Dosiervorrichtung als Stelleinrichtung einwirkt, so dass die Reduktionsmittelzugabe ins Abgas geregelt auf der Basis Signale der CO2-Sensoren erfolgen kann. Die Reduktionsmittelzugabe kann jedoch auch gesteuert auf der Basis von Kennlinien oder Kennfeldern vorgenommen werden, welche dem Steuergerät zu Verfügung stehen. Je nach Betriebspunkt wird die zu dosierende Reduktionsmittelmenge den Kennlinien oder Kennfeldern entnommen und die Dosiervorrichtung entsprechend angesteuert. Vorzugsweise erfolgt eine überstöchiometrische Zugabe des Reduktionsmittels.The device for the selective catalytic reduction of exhaust gases from an internal combustion engine contains a catalyst for the selective catalytic reduction of nitrogen oxides from exhaust gases of an internal combustion engine; a reducing agent metering device disposed upstream of the SCR catalyst for adding a urea-water solution as a reducing agent; and a controller for driving the reducing agent metering device. According to the invention, a first CO 2 sensor for detecting a CO 2 concentration upstream of the reducing agent metering device and a second CO 2 sensor for detecting a CO 2 concentration downstream of the reducing agent metering device are further arranged, and the controller controls the reducing agent metering device depending on a detected by the first and the second CO 2 sensor CO 2 concentration difference. In this way, the reducing agent can be metered as needed. In this case, the control device can also act as a control device, which acts on the reducing agent metering device as an adjusting device, so that the reducing agent addition to the exhaust gas can be regulated on the basis of signals from the CO 2 sensors. However, the addition of reducing agent can also be carried out in a controlled manner on the basis of characteristic curves or characteristic diagrams which are available to the control unit. Depending on the operating point, the amount of reducing agent to be metered is taken from the characteristic curves or characteristic diagrams and the metering device is activated accordingly. Preferably, a superstoichiometric addition of the reducing agent takes place.

Die als Reduktionsmittel durch die Reduktionsmittel-Dosiervorrichtung zugegebene Harnstoff-Wasser-Lösung (nachfolgend auch kurz als HWL bezeichnet) verdampft und hydrolysiert bei Anwesenheit von Wasser zu Ammoniak und Kohlendioxid. Dieses Nebenprodukt der Hydrolyse, nämlich Kohlendioxid, wird nun als Messgröße zur Regelung der Reduktionsmittel-Dosiervorrichtung verwendet. Über die erfasste Differenz der CO2-Konzentrationen vor und nach der Reduktionsmittel-Dosiervorrichtung kann aus dem bekannten Abgasmassenstrom die tatsächlich eingedüste Masse der HWL berechnet werden. Basierend auf dieser Information kann das Steuergerät dann die dosierende HWL-Menge ermitteln und die Dosiervorrichtung optimal ansteuern.The as a reducing agent through the reducing agent metering device added urea-water solution (hereinafter also referred to for short as HWL) evaporates and hydrolyzes in the presence of water to ammonia and carbon dioxide. This by-product of the hydrolysis, namely carbon dioxide, is now used as a parameter for controlling the reducing agent metering device. By means of the detected difference of the CO 2 concentrations before and after the reducing agent metering device, the actually injected mass of the HWL can be calculated from the known exhaust gas mass flow. Based on this information, the controller can then determine the metering HWL amount and control the metering optimally.

Vorzugsweise ist der zweite CO2-Sensor in einem solchen Abstand stromab der Reduktionsmittel-Dosiervorrichtung vorgesehen, dass an dem zweiten CO2-Sensor eine vollständige Hydrolyse des Reduktionsmittels erfolgt ist.Preferably, the second CO 2 sensor is provided at a distance downstream of the reducing agent metering device such that complete hydrolysis of the reducing agent has taken place on the second CO 2 sensor.

Der zweite CO2-Sensor kann sowohl stromauf des SCR-Katalysators als auch stromab des SCR-Katalysators angeordnet sein, da die Reaktionen im SCR-Katalysator die CO2-Konzentration im Abgasstrom nicht beeinflussen. Die Anordnung des zweiten CO2-Sensors stromab des SCR-Katalysators ist aufgrund der somit längeren Hydrolysestrecke für das Reduktionsmittel vorteilhaft.The second CO 2 sensor can be arranged both upstream of the SCR catalytic converter and downstream of the SCR catalytic converter, since the reactions in the SCR catalytic converter do not influence the CO 2 concentration in the exhaust gas flow. The arrangement of the second CO 2 sensor downstream of the SCR catalyst is advantageous because of the thus longer hydrolysis distance for the reducing agent.

In einer Ausgestaltung der Erfindung kann der erste CO2-Sensor auch ein virtueller Sensor sein, der die CO2-Konzentration aus dem Steuergerät bekannten Größen berechnet.In one embodiment of the invention, the first CO 2 sensor may also be a virtual sensor which calculates the CO 2 concentration from the controller known variables.

In einer weiteren Ausgestaltung der Erfindung sind der erste und der zweite CO2-Sensor als ein CO2-Differenzsensor mit hoher Empfindlichkeit ausgebildet. Diese Variante ist insbesondere dann von Vorteil, wenn die vom zweiten CO2-Sensor gemessene CO2-Konzentration nur wenig höher als die vom ersten CO2-Sensor erfasste ist.In a further embodiment of the invention, the first and the second CO 2 sensor are designed as a CO 2 difference sensor with high sensitivity. This variant is particularly advantageous when the second CO 2 sensor measured CO 2 concentration is only slightly higher than that detected by the first CO 2 sensor.

In einer weiteren bevorzugten Ausgestaltung der Erfindung ist ferner ein NH3-Sensor zum Erfassen einer NH3-Konzentration stromab des SCR-Katalysators angeordnet. In Kombination mit einem hinter dem SCR-Katalysator angeordneten NH3-Sensor zur Erfassung des NH3-Schlupfes nach dem SCR-Katalysator ist es möglich, den Anteil des im SCR-Katalysator umgesetzten bzw. eingespeicherten Ammoniaks zu quantifizieren.In a further preferred embodiment of the invention, an NH 3 sensor for detecting an NH 3 concentration downstream of the SCR catalyst is further arranged. In combination with an NH 3 sensor arranged behind the SCR catalytic converter for detecting the NH 3 slip after the SCR catalytic converter, it is possible to quantify the proportion of ammonia reacted or stored in the SCR catalytic converter.

Zusätzlich zu dem SCR-Katalysator ist bevorzugt ferner stromauf der Reduktionsmittel-Dosiervorrichtung ein bekannter Oxidationskatalysator vorgesehen.In addition to the SCR catalyst, a known oxidation catalyst is preferably also provided upstream of the reducing agent metering device.

In einer noch weiteren Ausgestaltung der Erfindung ist einer Reduktionsmitteldüse der Reduktionsmittel-Dosiervorrichtung außerdem eine Druckluftdüse zugeordnet, um das Reduktionsmittel mit Unterstützung von Druckluft einzudüsen.In yet another embodiment of the invention, a reducing agent nozzle of the reducing agent metering device is also associated with a compressed air nozzle to inject the reducing agent with the aid of compressed air.

Obige sowie weitere Merkmale und Vorteile der Erfindung werden aus der nachfolgenden Beschreibung eines bevorzugten, nicht-einschränkenden Ausführungsbeispiels der Erfindung unter Bezugnahme auf die beiliegenden Zeichnungen besser verständlich. Darin zeigt die einzige Figur eine schematische Darstellung des Aufbaus eines Abgasnachbehandlungssystems für einen Verbrennungsmotor gemäß einem bevorzugten Ausführungsbeispiel der vorliegenden Erfindung.The above and other features and advantages of the invention will become more apparent from the following description of a preferred, non-limiting embodiment of the invention with reference to the accompanying drawings. Therein, the single figure shows a schematic representation of the structure of an exhaust aftertreatment system for an internal combustion engine according to a preferred embodiment of the present invention.

In Fig. 1 ist schematisch der Aufbau eines Abgasnachbehandlungsystems eines Verbrennungsmotors 10, insbesondere eines direkteinspritzenden Dieselmotors, gemäß einem Ausführungsbeispiel der Erfindung veranschaulicht. In Fig. 1 ist dem Verbrennungsmotor die Bezugsziffer 10, einer Abgasleitung die Bezugsziffer 12, einem Oxidationskatalysator die Bezugsziffer 14 und einem SCR-Katalysator die Bezugsziffer 30 zugeordnet. Der Aufbau und die Funktionsweise des Verbrennungsmotors 10, des Oxidationskatalysators 14 und des SCR-Katalysators 30 sind dem Fachmann bekannt und werden hier nicht näher erläutert, da sie nicht Gegenstand der Erfindung sind.In Fig. 1, the structure of an exhaust aftertreatment system of an internal combustion engine 10, in particular a direct-injection diesel engine, according to an embodiment of the invention is schematically illustrated. In Fig. 1, the internal combustion engine is the reference numeral 10, an exhaust pipe the reference numeral 12, an oxidation catalyst, the reference numeral 14 and an SCR catalyst, the reference numeral 30 assigned. The structure and operation of the internal combustion engine 10, the oxidation catalyst 14 and the SCR catalyst 30 are known in the art and will not be explained in detail here, since they are not the subject of the invention.

Stromauf des SCR-Katalysators 30 zur selektiven katalytischen Reduktion der Stickoxide im Abgasstrom-aus dem Verbrennungsmotor 10 ist eine Reduktionsmittel-Dosiervorrichtung 15 vorgesehen. Diese Reduktionsmittel-Dosiervorrichtung 15 umfasst zum Beispiel einen Reduktionsmittelbehälter 20, eine Förderpumpe 22, ein Sperrventil 24 und eine in die Abgasleitung 12 ragende Reduktionsmitteldüse 16. Die Förderpumpe 22 und das Sperrventil 24 werden dabei durch ein Steuergerät 38 angesteuert.Upstream of the SCR catalyst 30 for the selective catalytic reduction of nitrogen oxides in the exhaust stream from the internal combustion engine 10, a reducing agent metering device 15 is provided. This reducing agent metering device 15 comprises, for example, a reducing agent tank 20, a feed pump 22, a check valve 24 and a reducing agent nozzle 16 protruding into the exhaust gas line 12. The feed pump 22 and the check valve 24 are actuated by a control unit 38.

Vorzugsweise ist der Reduktionsmitteldüse 16 in der Abgasleitung 12 eine Druckluftdüse 18 zugeordnet, die über ein Sperrventil 28 mit einer Druckluftquelle 26 verbunden ist. Auf diese Weise wird das Reduktionsmittel bevorzugt mit Unterstützung von Druckluft in die Abgasleitung 12 eingedüst. Alternativ ist es aber auch möglich, das Reduktionsmittel unverdünnt in flüssiger Form vor dem SCR-Katalysator 30 einzudüsen.Preferably, the reducing agent nozzle 16 in the exhaust pipe 12 is associated with a compressed air nozzle 18 which is connected via a check valve 28 to a compressed air source 26. In this way, the reducing agent is preferably injected into the exhaust pipe 12 with the aid of compressed air. Alternatively, it is also possible to inject the reducing agent undiluted in liquid form before the SCR catalyst 30.

Als Reduktionsmittel wird eine Harnstoff-Wasser-Lösung (HWL) verwendet. Diese HWL verdampft und hydrolysiert bei Anwesenheit von Wasser zu Ammoniak nach der folgenden Reaktionsgleichung:

         H2NCONH2 + H2O → 2 NH3 + CO2

As a reducing agent, a urea-water solution (HWL) is used. This HWL vaporizes and hydrolyzes in the presence of water to ammonia according to the following reaction equation:

H 2 NCONH 2 + H 2 O → 2 NH 3 + CO 2

Dabei entsteht aus 1 Mol Harnstoff neben den für die selektive katalytische Reduktion von Stickoxiden im SCR-Katalysator 30 benötigten 2 Mol Ammoniak auch 1 Mol Kohlendioxid. Dieses Nebenprodukt der Hydrolyse wird gemäß der vorliegenden Erfindung wie folgt als Messgröße zur Regelung der Reduktionsmittel-Dosiervorrichtung 15 verwendet.In addition to the 2 moles of ammonia required for the selective catalytic reduction of nitrogen oxides in the SCR catalyst 30, 1 mole of urea also produces 1 mole of carbon dioxide. This by-product of the hydrolysis is used according to the present invention as a measure for controlling the reducing agent metering device 15 as follows.

In der Abgasleitung 12 sind ein erster CO2-Sensor 32 stromauf der Reduktionsmitteldüse 16 der Reduktionsmittel-Dosiervorrichtung 15 sowie ein zweiter CO2-Sensor 34 stromab der Reduktionsmitteldüse 16 jeweils zum Erfassen einer CO2-Konzentration angeordnet. Der zweite CO2-Sensor 34 ist dabei bevorzugt in einem solchen Abstand hinter der Reduktionsmitteldüse 16 angeordnet, der für eine vollständige Hydrolyse der eingedüsten HWL erforderlich ist. Aus der Differenz der CO2-Konzentrationen nach und vor der Reduktionsmitteldüse 16 kann aus dem bekannten Abgasmassenstrom in der Abgasleitung 12 unter Voraussetzung einer vollständigen Hydrolyse der HWL einfach die eingedüste Masse der HWL berechnet werden. Basierend auf dieser Information steuert das Steuergerät 38 dann die Reduktionsmittel-Dosiervorrichtung 15 an.In the exhaust pipe 12, a first CO 2 sensor 32 upstream of the reducing agent nozzle 16 of the reducing agent metering device 15 and a second CO 2 sensor 34 downstream of the reducing agent 16 each for detecting a CO 2 concentration are arranged. The second CO 2 sensor 34 is preferably arranged at such a distance behind the reducing agent nozzle 16, which is required for complete hydrolysis of the injected HWL. From the difference between the CO 2 concentrations before and before the reducing agent nozzle 16, it is possible to simply calculate the injected mass of the HWL from the known exhaust gas mass flow in the exhaust gas line 12, assuming complete hydrolysis of the HWL. Based on this information, the controller 38 then controls the reductant metering device 15.

Dem Steuergerät 38 werden hierzu neben den Messwerten des ersten und des zweiten CO2-Sensors 32, 34 auch Messwerte des Verbrennungsmotors 10 und eines oder mehrerer Temperatursensoren 40 in der Abgasleitung 12 zugeführt.In addition to the measured values of the first and second CO 2 sensors 32, 34, the control unit 38 is also supplied with measured values of the internal combustion engine 10 and one or more temperature sensors 40 in the exhaust gas line 12.

Selbst wenn nur eine unvollständige Hydrolyse der HWL stattfindet, ist es mit dem erfindungsgemäßen System möglich, die Masse an hydrolysierter HWL zu berechnen. Aus dieser Größe ist dann direkt ableitbar, wie viel Ammoniak für den nach der Hydrolysestrecke angeordneten SCR-Katalysator 30 tatsächlich erzeugt worden ist. Somit eignet sich die erfindungsgemäße Sensorik 32, 34 auch zur Überwachung der Hydrolysegüte im Abgasnachbehandlungssystem.Even if only incomplete hydrolysis of the HWL takes place, it is possible with the system according to the invention to calculate the mass of hydrolyzed HWL. It is then directly deducible from this variable how much ammonia has actually been produced for the SCR catalytic converter 30 arranged after the hydrolysis section. Thus, the invention is suitable Sensors 32, 34 also for monitoring the quality of hydrolysis in the exhaust aftertreatment system.

In einer alternativen Ausführungsform der Erfindung ist der zweite CO2-Sensor 34 nicht stromauf des SCR-Katalysators 30 angeordnet, sondern nach diesem vorgesehen, wie durch die Bezugsziffer 34' in Fig. 1 angedeutet. Durch die Anordnung des zweiten CO2-Sensors 34' hinter dem SCR-Katalysator 30 wird die Hydrolysestrecke bis zur Messung der CO2-Konzentration verlängert, wodurch die Messgenauigkeit erhöht werden kann. Andererseits wird die CO2-Konzentration durch die Reaktionen im SCR-Katalysator 30 nicht beeinflusst.In an alternative embodiment of the invention, the second CO 2 sensor 34 is not disposed upstream of the SCR catalyst 30, but provided thereafter, as indicated by the reference numeral 34 'in Fig. 1. The arrangement of the second CO 2 sensor 34 'behind the SCR catalyst 30, the hydrolysis distance is extended to the measurement of the CO 2 concentration, whereby the measurement accuracy can be increased. On the other hand, the CO 2 concentration is not affected by the reactions in the SCR catalyst 30.

Des Weiteren ist stromab des SCR-Katalysators 30 in dem Ausführungsbeispiel von Fig. 1 auch ein NH3-Sensor 36 zur Erfassung eines NH3-Schlupfes nach dem SCR-Katalysator 30 vorgesehen, dessen Messwert ebenfalls dem Steuergerät 38 zugeleitet wird. Durch diesen zusätzlichen NH3-Sensor 36 ist es möglich, den Anteil des im SCR-Katalysator 30 umgesetzten bzw. eingespeicherten Ammoniak zu quantifizieren. Wird der Schlupf über dem NH3-Sensor 36 konstant gehalten, kann der SCR-Katalysator 30 kein Ammoniak mehr speichern. Die Differenz der NH3-Konzentrationen vor und nach dem SCR-Katalysator 30 ist somit ein direktes Maß für die Umsetzung im SCR-Katalysator 30 bzw. liefert Aussagen über den Zustand (z.B. Konvertierungsgrad über Lebensdauer) des SCR-Katalysators 30. Dabei wird die genannte NH3-Konzentration vor dem SCR-Katalysator 30 aus der obigen CO2-Messung berechnet.Furthermore, downstream of the SCR catalytic converter 30 in the exemplary embodiment of FIG. 1, an NH 3 sensor 36 is also provided for detecting an NH 3 slip after the SCR catalytic converter 30, the measured value of which is likewise fed to the control unit 38. This additional NH 3 sensor 36 makes it possible to quantify the proportion of ammonia reacted or stored in the SCR catalytic converter 30. If the slip over the NH 3 sensor 36 is kept constant, the SCR catalyst 30 can no longer store ammonia. The difference of the NH 3 concentrations before and after the SCR catalyst 30 is thus a direct measure of the conversion in the SCR catalyst 30 or provides statements about the state (eg degree of conversion over life) of the SCR catalyst 30 calculated NH 3 concentration before the SCR catalyst 30 from the above CO 2 measurement.

Während die vorliegende Erfindung oben anhand eines bevorzugten Ausführungsbeispiels unter Bezugnahme auf die beiliegende Zeichnung beschrieben worden ist, ist es selbstverständlich, dass verschiedene Varianten und Modifikationen daran vorgenommen werden können, ohne den Schutzumfang der Erfindung zu verlassen, wie er durch die anhängenden Ansprüche definiert ist.While the present invention has been described above with reference to a preferred embodiment with reference to the accompanying drawings, it is to be understood that various variations and modifications may be made thereto without departing from the scope of the To leave invention as defined by the appended claims.

Zum Beispiel sind der erste und der zweite CO2-Sensor 32 und 34 bzw. 34' in Fig. 1 als separate Sensoren ausgebildet. Alternativ ist es auch möglich, einen CO2-Differenzsensor mit hoher Empfindlichkeit einzusetzen, dessen Messpunkte den Sensorpositionen des oben beschriebenen Ausführungsbeispiels entsprechen. Die Verwendung eines solchen CO2-Differenzsensors kann deutliche Vorteile bieten, wenn die Erhöhung der CO2-Konzentration an der Stelle des zweiten CO2-Sensors 34, 34' im Vergleich zur Stelle des ersten CO2-Sensors 32 relativ gering ist.For example, the first and second CO 2 sensors 32 and 34 and 34 'in FIG. 1 are formed as separate sensors. Alternatively, it is also possible to use a CO 2 difference sensor with high sensitivity whose measuring points correspond to the sensor positions of the embodiment described above. The use of such a CO 2 differential sensor can provide significant benefits if the increase in CO 2 concentration at the location of the second CO 2 sensor 34, 34 'is relatively small compared to the location of the first CO 2 sensor 32.

Als weitere Alternative zu dem oben beschriebenen Ausführungsbeispiel von Fig. 1 ist es auch möglich, anstelle des ersten CO2-Sensors 32 einen virtuellen ersten CO2-Sensor zu benutzen. Dieser virtuelle erste CO2-Sensor berechnet die CO2-Konzentration vor der Reduktionsmittel-Dosiervorrichtung 15 unter der Voraussetzung einer vollständigen Verbrennung des im Verbrennungsmotor 10 eingespritzten Kraftstoffes aus den im Steuergerät 38 bekannten Größen Luftmasse und Kraftstoffmasse. Diese Annahme ist zulässig, da im Dieselmotor 10 nur ein sehr geringer Anteil des Kraftstoffes nicht umgesetzt und in Form von HC- und CO-Emissionen emittiert wird. Ist der erste CO2-Sensor 32 zudem stromab eines Oxidationskatalysators 14 vorgesehen, enthält die CO2-Konzentration dort auch das Kohlendioxid aus der Nachoxidation der unverbrannten Abgasanteile im Oxidationskatalysator 14.As a further alternative to the embodiment of FIG. 1 described above, it is also possible to use a virtual first CO 2 sensor instead of the first CO 2 sensor 32. This virtual first CO 2 sensor calculates the CO 2 concentration in front of the reducing agent metering device 15 on the assumption of complete combustion of the fuel injected in the internal combustion engine 10 from the variables air mass and fuel mass known in the control unit 38. This assumption is permissible because in the diesel engine 10 only a very small proportion of the fuel is not reacted and emitted in the form of HC and CO emissions. If the first CO 2 sensor 32 is also provided downstream of an oxidation catalytic converter 14, the CO 2 concentration there also contains the carbon dioxide from the post-oxidation of the unburned exhaust gas components in the oxidation catalytic converter 14.

Claims (16)

Vorrichtung zur selektiven katalytischen Reduktion von Abgasen aus einem Verbrennungsmotor, mit
einem Katalysator (30) zur selektiven katalytischen Reduktion von Stickoxiden aus Abgasen eines Verbrennungsmotors (10);
einer Reduktionsmittel-Dosiervorrichtung (15), die stromauf des SCR-Katalysators (30) angeordnet ist, zum Zugeben einer Harnstoff-Wasser-Lösung als Reduktionsmittel; und
einem Steuergerät (38) zum Ansteuern der Reduktionsmittel-Dosiervorrichtung (15),
dadurch gekennzeichnet, dass
ferner ein erster CO2-Sensor (32) zum Erfassen einer CO2-Konzentration stromauf der Reduktionsmittel-Dosiervorrichtung (15) angeordnet ist;
dass ferner ein zweiter CO2-Sensor (34, 34') zum Erfassen einer CO2-Konzentration stromab der Reduktionsmittel-Dosiervorrichtung (15) angeordnet ist; und
dass das Steuergerät (38) die Reduktionsmittel-Dosiervorrichtung (15) in Abhängigkeit von einer durch den ersten und den zweiten CO2-Sensor (32, 34, 34') erfassten CO2-Konzentrationsdifferenz ansteuert.Device for the selective catalytic reduction of exhaust gases from an internal combustion engine, with
a catalyst (30) for the selective catalytic reduction of nitrogen oxides from exhaust gases of an internal combustion engine (10);
a reducing agent metering device (15) disposed upstream of said SCR catalyst (30) for adding a urea-water solution as a reducing agent; and
a control device (38) for actuating the reducing agent metering device (15),
characterized in that
a first CO 2 sensor (32) for detecting a CO 2 concentration upstream of the reducing agent metering device (15) is arranged;
that a second CO 2 sensor (34, 34 ') for detecting a CO 2 concentration downstream of the reducing agent metering device (15) is arranged; and
in that the control unit (38) actuates the reducing agent metering device (15) as a function of a CO 2 concentration difference detected by the first and the second CO 2 sensors (32, 34, 34 '). Vorrichtung nach Anspruch 1,
dadurch gekennzeichnet, dass
der zweite CO2-Sensor (34, 34') in einem solchen Abstand stromab der Reduktionsmittel-Dosiervorrichtung (15) vorgesehen ist, dass an dem zweiten CO2-Sensor eine vollständige Hydrolyse des Reduktionsmittels erfolgt ist.Device according to claim 1,
characterized in that
the second CO 2 sensor (34, 34 ') is provided at such a distance downstream of the reducing agent metering device (15) that complete hydrolysis of the reducing agent has taken place on the second CO 2 sensor. Vorrichtung nach Anspruch 1 oder 2,
dadurch gekennzeichnet, dass
der zweite CO2-Sensor (34) stromauf des SCR-Katalysators (30) angeordnet ist.Apparatus according to claim 1 or 2,
characterized in that
the second CO 2 sensor (34) is disposed upstream of the SCR catalyst (30). Vorrichtung nach Anspruch 1 oder 2,
dadurch gekennzeichnet, dass
der zweite CO2-Sensor (34') stromab des SCR-Katalysators (30) angeordnet ist.Apparatus according to claim 1 or 2,
characterized in that
the second CO 2 sensor (34 ') is disposed downstream of the SCR catalyst (30). Vorrichtung nach einem der Ansprüche 1 bis 4,
dadurch gekennzeichnet, dass
der erste CO2-Sensor (32) ein virtueller Sensor ist, der die CO2-Konzentration aus dem Steuergerät (38) bekannten Größen berechnet.Device according to one of claims 1 to 4,
characterized in that
the first CO 2 sensor (32) is a virtual sensor that calculates the CO 2 concentration from the controller (38) known sizes. Vorrichtung nach einem der Ansprüche 1 bis 4,
dadurch gekennzeichnet, dass
der erste und der zweite CO2-Sensor (32, 34, 34') als ein CO2-Differenzsensor ausgebildet sind.Device according to one of claims 1 to 4,
characterized in that
the first and second CO 2 sensors (32, 34, 34 ') are designed as a CO 2 difference sensor. Vorrichtung nach einem der Ansprüche 1 bis 6,
dadurch gekennzeichnet, dass
ferner ein NH3-Sensor (36) zum Erfassen einer NH3-Konzentration stromab des SCR-Katalysators (30) angeordnet ist.Device according to one of claims 1 to 6,
characterized in that
Further, an NH 3 sensor (36) for detecting a NH 3 concentration downstream of the SCR catalyst (30) is arranged. Vorrichtung nach einem der Ansprüche 1 bis 7,
dadurch gekennzeichnet, dass
ferner stromauf der Reduktionsmittel-Dosiervorrichtung (15) ein Oxidationskatalysator vorgesehen ist.Device according to one of claims 1 to 7,
characterized in that
further upstream of the reducing agent metering device (15) is provided an oxidation catalyst. Vorrichtung nach einem der Ansprüche 1 bis 8,
dadurch gekennzeichnet, dass
einer Reduktionsmitteldüse (16) der Reduktionsmittel-Dosiervorrichtung (15) eine Druckluftdüse (18) zugeordnet ist, um das Reduktionsmittel mit Unterstützung von Druckluft einzudüsen.Device according to one of claims 1 to 8,
characterized in that
a reducing agent nozzle (16) of the reducing agent metering device (15) is associated with a compressed air nozzle (18) to inject the reducing agent with the aid of compressed air. Verfahren zur selektiven katalytischen Reduktion von Abgasen aus einem Verbrennungsmotor, bei welchem Stickoxide aus Abgasen eines Verbrennungsmotors (10) in einem Katalysator (30) selektiv katalytisch reduziert werden; und
stromauf des SCR-Katalysators (30) eine Harnstoff-Wasser-Lösung als Reduktionsmittel zugegeben wird;
dadurch gekennzeichnet, dass
eine erste CO2-Konzentration stromauf der Reduktionsmittel-Zugabe erfasst wird;
dass eine zweite CO2-Konzentration stromab der Reduktionsmittel-Zugabe erfasst wird; und
dass die Reduktionsmittel-Zugabe in Abhängigkeit von einer erfassten Differenz der ersten und der zweiten CO2-Konzentration eingestellt wird.Method for the selective catalytic reduction of exhaust gases from an internal combustion engine, in which nitrogen oxides are selectively catalytically reduced from exhaust gases of an internal combustion engine (10) in a catalytic converter (30); and
upstream of the SCR catalyst (30), a urea-water solution is added as a reducing agent;
characterized in that
a first CO 2 concentration is detected upstream of the reductant addition;
that a second CO 2 concentration is detected downstream of the reducing agent addition; and
that the reducing agent addition is adjusted in dependence on a detected difference of the first and the second CO 2 concentration. Verfahren nach Anspruch 10,
dadurch gekennzeichnet, dass
an der Stelle der zweiten CO2-Konzentration eine vollständige Hydrolyse des zugegeben Reduktionsmittels erfolgt ist.Method according to claim 10,
characterized in that
at the point of the second CO 2 concentration, a complete hydrolysis of the added reducing agent has taken place. Verfahren nach Anspruch 10 oder 11,
dadurch gekennzeichnet, dass
die zweite CO2-Konzentration stromauf des SCR-Katalysators (30) erfasst wird.Method according to claim 10 or 11,
characterized in that
the second CO 2 concentration is detected upstream of the SCR catalyst (30). Verfahren nach Anspruch 10 oder 11,
dadurch gekennzeichnet, dass
die zweite CO2-Konzentration stromab des SCR-Katalysators (30) erfasst wird.Method according to claim 10 or 11,
characterized in that
the second CO 2 concentration is detected downstream of the SCR catalyst (30). Verfahren nach einem der Ansprüche 10 bis 13,
dadurch gekennzeichnet, dass
die erste CO2-Konzentration aus bekannten Größen berechnet wird.Method according to one of claims 10 to 13,
characterized in that
the first CO 2 concentration is calculated from known quantities. Verfahren nach einem der Ansprüche 10 bis 14,
dadurch gekennzeichnet, dass
ferner eine NH3-Konzentration stromab des SCR-Katalysators (30) erfasst wird.Method according to one of claims 10 to 14,
characterized in that
Further, an NH 3 concentration downstream of the SCR catalyst (30) is detected. Verfahren nach einem der Ansprüche 10 bis 15,
dadurch gekennzeichnet, dass
das Reduktionsmittel mit Unterstützung von Druckluft eingedüst wird.Method according to one of claims 10 to 15,
characterized in that
the reducing agent is injected with the aid of compressed air.
EP06006664A 2005-04-01 2006-03-30 Process and device for the selective catalytic reduction of exhaust gases from a combustion engine Withdrawn EP1710010A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE102005014891A DE102005014891A1 (en) 2005-04-01 2005-04-01 Selective catalytic reduction of nitrogen oxides in engine exhaust gas comprises adjusting the amount of reducing agent injected as a function of the difference between two carbon dioxide concentrations

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EP1710010A1 true EP1710010A1 (en) 2006-10-11

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2929329A1 (en) * 2008-03-28 2009-10-02 Peugeot Citroen Automobiles Sa Reducing agent e.g. urea, quantity determining method for exhaust line in diesel engine of motor vehicle, involves calculating quantity of injected reducing agent e.g. urea, based on difference between two exhaust gas richness measurements
CN101240729B (en) * 2008-02-20 2012-04-18 孙靖茗 Diesel automobile exhaust and urea box reflector

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108661758A (en) * 2017-04-01 2018-10-16 中国船舶重工集团公司第七研究所 SCR supplies spraying system and ship

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998045581A1 (en) * 1997-04-04 1998-10-15 Clean Diesel Technologies, Inc. REDUCING NOx EMISSIONS FROM AN ENGINE WHILE MAXIMIZING FUEL ECONOMY
EP1338770A2 (en) * 2002-02-25 2003-08-27 DaimlerChrysler AG Exhaust gas purification device for an internal combustion engine
WO2004000443A1 (en) * 2002-06-19 2003-12-31 E.I. Du Pont De Nemours And Company Method and apparatus for reducing a nitrogen oxide, and control thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998045581A1 (en) * 1997-04-04 1998-10-15 Clean Diesel Technologies, Inc. REDUCING NOx EMISSIONS FROM AN ENGINE WHILE MAXIMIZING FUEL ECONOMY
EP1338770A2 (en) * 2002-02-25 2003-08-27 DaimlerChrysler AG Exhaust gas purification device for an internal combustion engine
WO2004000443A1 (en) * 2002-06-19 2003-12-31 E.I. Du Pont De Nemours And Company Method and apparatus for reducing a nitrogen oxide, and control thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101240729B (en) * 2008-02-20 2012-04-18 孙靖茗 Diesel automobile exhaust and urea box reflector
FR2929329A1 (en) * 2008-03-28 2009-10-02 Peugeot Citroen Automobiles Sa Reducing agent e.g. urea, quantity determining method for exhaust line in diesel engine of motor vehicle, involves calculating quantity of injected reducing agent e.g. urea, based on difference between two exhaust gas richness measurements

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